Chemistry Class 10 Solutions Chemical Reactions And Equations

1.Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.
Solution :

1.  Evolution of gas.
   For example: When sodium carbonate reacts with dilute hydrochloric acid, carbon dioxide gas is evolved.
2.  Formation of a precipitate.
   For example: When potassium iodide solution is added to a solution of lead nitrate, yellow precipitate of lead iodide is formed.

2(a) Aluminium hydroxide reacts with sulphuric acid to form aluminium sulphate and water. .Write a balanced equation for this reaction.
(b) Balance the following chemical equation :
MnO2 + HCl —–> MnCl2 + Cl2 + H2O
Solution :
(a) 2Al(OH)3+ 3H2SO4 —–> Al2(SO4)3+ 6H2O
(b) MnO2+ 4HCl —–> MnCl2+ Cl2 + 2H2O

3. Write the balanced equations for the following reactions, and add the state symbols :
(a)  Magnesium carbonate reacts with hydrochloric acid to produce magnesium chloride, carbon dioxide and water.
(b) Sodium hydroxide reacts with sulphuric acid to produce sodium sulphate and water.
Solution :
(a) MgCO3 (s) + 2HCl (aq) MgCl2 (aq) + CO2 (g) + H2O (l)
(b) 2NaOH (aq) + H2SO4 (aq) Na2SO4 (aq) + 2H2O (l)

4. Carbon monoxide reacts with hydrogen under certain conditions to form methanol (CH3OH). Write a balanced chemical equation for this reaction indicating the physical states of reactants and product as well as the conditions under which this reaction takes place.
Solution :
The conditions for this reaction to take place are: a pressure of 300 atmospheres (written as 300 atm), a temperature of 300oC, and a catalyst which is a mixture of zinc oxide and chromium oxide (ZnO + CrO3).

5.a) Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation
for this reaction and indicate the evolution of gas.
(b) Rewrite the following information in the form of a balanced chemical equation :
Magnesium burns in carbon dioxide to form magnesium oxide and carbon.
Solution :
(a) 2KClO3
(s) 2KCl (s) + 3O2 (g)
(b) 2Mg + CO2 —–> 2MgO + C